In order to
avoid unexpected (unpredictable, experientially unsafe) confrontations with others and/or to provide more processing time.

Elaboration
People on the spectrum may experience a threat when strangers appear at the front door ‘suddenly’ and/or ‘unexpectedly’. The counter-measures differ, depending on the living situation, but are the same in principle. Some homes have a view on a front, or back-garden, others on the gallery of a flat building, or may be situated directly on a street. In each situation the ‘sudden’ appearance of someone can elicit unease because of its unpredictability. Adequate fencing of the garden or a gate or porch which can be closed or for instance can sound a signal when opened, are therefore advisable.

Additionally or alternatively other measures can be taken to prepare for such encounters, for instance with the aid of a mirror, a door-phone or a camera. A foyer or vestibule usually is a good idea too; they can be used to ease visitors into the house.

Such preparation is necessary in order to augment predictability and experienced safety. Apart from general limitations in social interaction and communication, a limited Theory of Mind may also be involved. Extra processing time then serves different purposes, among which is time to interpret the intentions of others. Face recognition troubles can add to the confusion: family friends and acquaintances may be perceived as strangers.

People who live (semi-)independently may have the above mentioned problems (see context independent living). The advantage over people on the spectrum who reside in a mental health facility is their greater ego-strength which enables them to devise ways to deal with their autistic drawbacks. One might, for instance, agree with regular visitors that they never come unannounced and/or that they call when they’re (almost) there. Solutions for unknown or unannounced visitors may include a sign explaining one has to wait a bit longer. Possibly one might find neighbors willing to open their door for parcels etc. or even serve as a regular delivery address. These examples are meant to get the point across that people who live independently are usually quite capable of recognizing their weaknesses and finding solutions which befit them and their situation.